1. Field of the Invention
The present invention relates to a light emitting diode (LED) array driving apparatus, and more particularly, to an LED array driving apparatus employing a single ended primary inductance converter (SEPIC) type of a direct current-direct current (DC-DC) converting part and capable of protecting an LED and a driving circuit from an overvoltage applied to the LED and controlling a duty of an output signal of a pulse width modulation integrated circuit (PWM IC) to be 0%.
2. Description of the Related Art
A cold cathode fluorescent lamp (CCFL) used as a light source of a conventional liquid crystal display (LCD) employs mercury gas, which may trigger environmental pollution. Besides, the CCFL is slow in response rate, low in color reproducibility and inappropriate for a smaller-sized and lighter-weight liquid crystal display (LCD) panel.
In contrast, a light emitting diode (LED) is environment-friendly, high in response rate with several nano seconds, thus effective for a video signal stream and capable of being impulsively driven. Moreover, the LED can reproduce color by 100% and alter brightness and color temperature by adjusting light amount of red, green and blue LEDs. Also, the LED carries advantages suitable for the smaller-sized and lighter-weight LCD panel. Therefore, of late, the LED has been actively employed as a backlight source of the LCD panel.
As described above, in a case where an LED array having a plurality of LEDs connected to one another is utilized in the liquid crystal display (LCD) backlight employing the LED, a driving circuit for driving the LED array requires a direct current-direct current (DC-DC) converter converting an input voltage inputted from the outside into a voltage suitable for driving the LED array, and a driving circuit supplying a predetermined constant current to the LED array. Moreover, the LED array driving circuit additionally requires a dimming circuit which enables a user to adjust brightness and color temperature arbitrarily or adjust brightness of the LEDs for e.g., temperature compensation.
Particularly, the DC-DC converter applied to a conventional LED array driving apparatus is formed of a boost-type DC-DC converter which increases an input voltage level to output or a buck-type DC-DC converter which decreases an input voltage level to output. Therefore, when the LED array driving apparatus is applied to an application apparatus having input voltages different from each other, or a voltage for driving the LEDs is changed in magnitude, the LED array driving apparatus cannot be applied as such.